Circulating fluidized bed reactor

Abstract

A circulating fluidized bed reactor includes a furnace, defined by a substantially vertical and planar first wall, and a particle separator having a return duct adjacent to the first wall. In the lower part of the return duct is arranged a gas seal adjacent to a planar tube wall, which wall is the planar wall or a wall defining a space in gas flow connection with the furnace. The width of the horizontal cross section of the lower part of the return duct, measured in the direction of the first wall, is larger than its depth, measured perpendicular to the width. The gas seal includes a seal structure that includes water tubes bent from the tube wall.

We claim:  
     
       1. A circulating fluidized bed reactor, comprising: 
       a furnace, a lower part of which is provided with fluidizing gas nozzles for fluidizing bed material to be fed to the furnace, the furnace being defined by a substantially vertical and planar first wall;  
       a particle separator for separating bed material from the gas discharged from the reactor;  
       a return duct for bed material separated in the particle separator, arranged in connection with said first wall, and having a lower part;  
       a gas seal arranged in the lower part of the return duct, preventing gas from flowing from the furnace to the return duct; and  
       a receiving space defined by a planar water tube wall, which receiving space may comprise the furnace, whereby the water tube wall is the first wall, or a space in gas flow connection with the furnace,  
       wherein the gas seal (i) is arranged in connection with the water tube wall defining the receiving space in such a way that a horizontal cross-sectional width of the lower part of the return duct measured in the direction of the first wall is larger than the depth perpendicular to the width and (ii) has a seal structure comprising water tubes joined to each other and formed by bending water tubes from the water tube wall defining the receiving space.  
     
     
       2. A circulating fluidizing be reactor according to  claim 1 , wherein the seal structure separates a distinct portion from the bed of circulating material being formed in the lower part of the return duct and forms a seal channel, defined by the seal structure, the lower part of which is provided with flow means connected to the return duct, and a substantially vertical front wall, the upper part of which is in flow connection with return means formed in the water tube wall defining the receiving space. 
     
     
       3. A circulating fluidized bed reactor according to  claim 2 , wherein the seal structure comprises a side wall connected to the front wall, and the water tubes in the water tube wall defining the receiving space are bent to cool the side wall and to form a supporting structure for the side wall. 
     
     
       4. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the seal structure comprises water tubes joined to each other, bent from the water tubes in the water tube wall defining the receiving space, supporting the water tube wall and preventing the return means from weakening the water tube wall. 
     
     
       5. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the seal structure comprises two side walls, a rear wall and a roof portion. 
     
     
       6. A circulating fluidized bed reactor in accordance with  claim 5 , wherein the lower part of the rear wall is in flow connection with the return duct. 
     
     
       7. A circulating fluidized bed reactor in accordance with  claim 5 , wherein a portion of water tubes in the water tube wall defining the receiving space is bent to extend from the front wall to the side wall and therefrom, via the roof portion, back to the water tube wall defining the receiving space. 
     
     
       8. A circulating fluidized bed reactor in accordance with  claim 5 , wherein a portion of water tubes in the water tube wall is bent to extend from the front wall to the side wall and therefrom, via the rear wall and the roof portion, back to the water tube wall defining the receiving space. 
     
     
       9. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the horizontal cross section of the seal channel is substantially rectangular and the width measured in the direction of the first wall is at least 1.5 times the depth perpendicular to the width. 
     
     
       10. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the gas seal comprises at least two adjacently disposed seal channels parallel to the first wall and in communication with a common return duct. 
     
     
       11. A circulating fluidized bed reactor in accordance with  claim 10 , wherein the total width of the adjacent seal channels is at least approximately three times their depth. 
     
     
       12. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the lower part of the return duct is provided, in the direction of the first wall defining the furnace, with a seal channel of the gas seal abreast of a down leg conducting bed material from the particle separator to the seal channel. 
     
     
       13. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the return duct is formed of planar water tube panels. 
     
     
       14. A circulating fluidized bed reactor in accordance with  claim 13 , wherein an extension of the wall on the furnace side of the return duct forms the rear wall of the seal channel. 
     
     
       15. A circulating fluidized bed reactor in accordance with  claim 13 , wherein the seal channel is at least partially arranged between the extension of the wall on the furnace side of the return duct and the first wall defining the furnace. 
     
     
       16. A circulating fluidized bed reactor in accordance with  claim 13 , wherein one of the water tube walls forming the return duct is a section of the first wall defining the furnace. 
     
     
       17. A circulating fluidized bed reactor in accordance with  claim 3 , wherein the horizontal cross section of the lower part of the return duct is rectangular and its width measured in the direction of the first wall is at least approximately twice the depth perpendicular thereto.